1. Field of the Invention
The present invention relates to an image display device and method which displays a two-dimensional radiological image acquired by simple imaging and a tomographic image acquired by tomography, such as tomosynthesis imaging, and a program that causes a computer to perform an image display method.
2. Description of the Related Art
A medical image, such as a radiological image, is displayed and image diagnosis is performed with reference to a two-dimensional radiological image acquired by simple imaging and a tomographic image acquired by tomography using, for example, a CT device, an MRI device, or a tomosynthesis imaging device. For example, in order to perform diagnostic breast imaging, it is checked whether there is a lesion (tumor or calcification) in the breast, with reference to a two-dimensional radiological image which is acquired by simple imaging in various imaging directions, such as cranio-caudal (CC) imaging which emits radiation from the top to capture an image, medial-lateral (ML) imaging which emits radiation from the side to capture an image, and mediolateral-oblique (MLO) imaging which emits radiation in an oblique direction to capture an image, and a tomographic image which is generated by reconstructing a plurality of radiological images acquired by tomosynthesis imaging in each imaging direction.
Tomosynthesis imaging is an imaging method which irradiates the subject in a plurality of different directions to capture images while moving a radiation source and reconstructs the acquired image to obtain an image in which a desired tomographic plane is emphasized. In tomosynthesis imaging, the radiation source is moved parallel to the radiation detector or is moved in a circle or an arc of an ellipse, according to the characteristics of an imaging device or a necessary tomographic image, and the images of the subject are captured at a plurality of irradiation positions with different irradiation angles to acquire a plurality of radiological images. Then, the radiological images are reconstructed by a back projection method, such as a simple back projection method or a filtered back projection method, to generate a tomographic image.
The two-dimensional radiological image has the advantages of high consistency, high sharpness, and ease of comparison with the previous images over the tomographic image. Therefore, cross-referencing between the two-dimensional radiological image and the tomographic image is performed as follows. First, the two-dimensional radiological image is displayed on a display device, such as a liquid crystal monitor, and image diagnosis is performed. A position which is considered as a lesion on the two-dimensional radiological image is clicked and designated. Then, the tomographic image in which an area in the vicinity of the lesion is enlarged is displayed. In addition, in some cases, the two-dimensional radiological image and the tomographic image corresponding to the imaging direction of the two-dimensional radiological image are simultaneously displayed on the display device for cross-referencing. In any case, the tomographic image is displayed while the tomographic planes are automatically or manually switched.
A plurality of tomographic images are acquired by tomography such as tomosynthesis imaging. However, since the tomographic images include the tomographic image of the tomographic plane including, for example, the lesion and a tomographic image of a tomographic plane without including the lesion, the user, such as the doctor who performs image diagnosis, needs to read a plurality of tomographic images while switching the tomographic images. Therefore, when image diagnosis is performed with reference to both the two-dimensional radiological image and the tomographic image, the operation is more complicated than when only the two-dimensional radiological image is used. As a result, it takes a long time to perform diagnosis.
In order to solve the problems, a method has been proposed which receives a designated area of interest, such as a lesion, on a displayed two-dimensional radiological image, compares the image of the area of interest with the image of a corresponding area corresponding to the area of interest using image analysis, detects a tomographic image in which the image of the corresponding area is similar to the image of the area of interest on the basis of the analysis result, detects a tomographic image in which the image of a corresponding position is similar to the image of the area of interest when the area of interest is designated in the two-dimensional radiological image, and displays the tomographic image (see JP2012-245060A).
In addition, a method has been proposed which generates a maximum intensity projection (MIP) image or a minimum intensity projection (MinIP) image (hereinafter, referred to as an MIP image) from a tomographic image acquired by CT, using a projection method, such as an MIP method or an MinIP method, creates a depth information table in which depth information indicating the position of a pixel, which has the brightness value of the MIP image, in a basic tomographic image in the depth direction is stored for each MIP image, specifies the depth information of a designated position with reference to the depth table when an arbitrary position on the MIP image is designated, and displays the tomographic image of the tomographic plane at the depth indicated by the depth information (see JP2011-139788A).